Report on the Agricultural Experiment Stations, 1952 Page: 71
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RESEARCH IN LIVESTOCK PRODUCTION 71
a fourth was above average in daily gain. Techniques for performance
and progeny testing, now widely used by the experiment stations,
are constantly being improved through research.
Records obtained in bull-testing trials by the Oregon station (coop.
USDA) indicate that calves which are large at birth are likely to
reach slaughter weight earlier and use the least feed. Bull calves
gained 15 percent faster than heifers and required about 19 percent
less feed (total digestible nutrients) to produce each 100 pounds of
gain. There was little or no relationship between rate of gain and
type scores at weaning age; hence the conclusion that breeding stock
can be selected for rapid gains and good feed economy without sacrificing
Other research by the Texas, Wyoming, Colorado, and Ohio stations
is directed toward finding some biochemical or physiological
measure of genetic differences in gaining ability and feed economy of
beef cattle. In studies of the blood characteristics of bull calves, the
Texas station (coop. USDA) found that the levels of protein-bound
iodine (an index of thyroid activity) were negatively correlated with
daily gain in the feed lot, but showed a high positive correlation with
feed consumed per pound of gain. Calves making the highest and
most efficient gains had the lowest iodine values. Further research
is under way to establish the optimum levels of blood iodine for
cattle of different breeds and ages, and under varying environmental
In 196-day feeding tests over a 3-year period, the New Mexico
station (coop. USDA) found that compact steer calves required about
4 percent less feed (total digestible nutrients) to produce a pound of
gain, and gained 8 percent more in relation to their initial weight
than large-type steers.
Early- versus late-castrated steers
The best age at which to castrate bull calves for maximum
production of meat at lowest cost has been studied by the Ohio
station. Results to date show that weanling calves fed as bulls
for a period of 252 days gained about 12 percent more per day at
8 percent less cost than steer calves. Although the bulls had slightly
lower dressing percentages than the steers because they had heavier
heads and hides, they yielded a 3.8-percent higher portion of edible
meat. Steer carcasses carried considerably more finish than bull
carcasses and showed a 5-percent higher fat trim. The meat from
bulls and steers was found to be equally tender when aged for 15
days. Steers castrated at 1 month or 6 months of age made similar
records with respect to rate and cost of gain and carcass quality.
Late castration of calves will allow breeders to do a better job of
selecting young bulls for breeding purposes.
Needs of weanling pigs for amino acids
Single-stomached animals such as the pig are more specific in their
requirements for amino acids than are ruminants, which, with the
help of the rumen micro-organisms can synthesize any or all of the
amino acids needed. Since few protein feeds provide a complete
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United States. Office of Experiment Stations. Report on the Agricultural Experiment Stations, 1952, book, January 1953; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc5990/m1/73/: accessed October 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.